The proposed research examines the role of community coalitions in supporting the high-quality implementation of evidence-based prevention programs (EBPs) and reducing early substance use and abuse. Communities often implement duplicative and non-systematic programming that lacks empirical support while overlooking numerous EBPs that are replicable and lead to substantial cost-savings. For communities interested in a focused, systematic public health approach to the prevention of alcohol, tobacco and other drugs (ATOD), Communities That Care (CTC) provides community coalitions with an evidence-based process to coordinate the assessment, planning, and implementation of EBPs. To better understand the conditions necessary for coalitions to successfully prevent drug abuse, the proposed research examines the relations between CTC coalition functioning, EBP implementation support, and youth outcomes. The first aim focuses on longitudinally examining whether broad or specific aspects of coalition functioning influence EBP implementation support. The relations between coalition functioning and EBP implementation support will be examined across a 3-year period using cross lagged panel models that capture reciprocal causation. These models can strengthen causal inferences because they simultaneously model how changes in coalition functioning influence EBP implementation support and vice versa over time. The second aim examines the influence of coalitions'EBP implementation support on youth outcomes. Previous evaluations of CTC in Pennsylvania indicate that youth in CTC communities implementing EBPs have lower rates of delinquency and risk across adolescence than youth in non-CTC communities. The second aim will build on this evaluation by examining whether the degree of implementation support provided by the CTC coalition impacts youth outcomes. The proposed research uses a multi-reporter approach that ensures the independence of each data source. Coalition functioning and EBP implementation support are measured annually as part of a process evaluation of CTC coalitions in Pennsylvania;approximately 900 board members report on their CTC coalition functioning each year. Measures of coalition functioning are also captured from the perspective of technical assistance providers who support each coalition. Youth outcomes are measured using the CTC Youth Survey, which is administered biennially as an anonymous questionnaire to approximately 90,000 6th, 8th, 10th and 12th graders in 160 Pennsylvania school districts. The survey assesses risk and protective factors related to substance use and delinquency, as well as rates of drug use and antisocial behavior.